Lewin Diaz was the Twins' biggest ticket item from 2013 international spending, signing for $1.4 million out of the Dominican Republic as a 16-year-old. Baseball America referred to the 6-foot-4 first baseman's "big, lumbering body" and wrote that "his value is all in his bat." That player type normally doesn't interest the Twins, but Diaz made his pro debut last season in the Dominican Summer League and batted .257/.385/.451 with 18 extra-base hits and 26 walks in 43 games.

Rookie-ball numbers are to be taken with large grains of salt and the Dominican Summer League is even a step down from that in terms of competition, so Diaz's actual numbers there don't mean much. However, the fact that he hit a bunch of homers and doubles while walking more than he struck out is certainly a positive first impression by a 17-year-old. He was signed for his bat and so far his bat looks pretty good.

For some context his Isolated Power was 125 percent higher than the Dominican Summer League average and he drew 45 percent more walks than the DSL as a whole. When your body type is compared to guys like David Ortiz and Ryan Howard at age 16 you obviously need to hit a ton to make it to the big leagues, which Diaz will look to continue doing at rookie-ball in his American debut this year.

Signed out of Taiwan for $220,000 in late 2012 as an 18-year-old, Chih-Wei Hu had a strong debut in the rookie-level Gulf Coast League in 2013 with a 2.45 ERA and 39/8 K/BB ratio in 37 innings. He began last season one level higher at rookie-level Elizabethton, but after just three impressive starts there the Twins decided to promote him to low Single-A. Hu didn't miss a beat, holding Midwest League hitters to a .201 batting average and zero homers in 55 innings.

Hu draws the most praise for his mature approach, strike-throwing ability, and quality changeup, but the 6-foot-1 right-hander is hardly a soft-tosser and can reach the mid-90s with his fastball at times. He has a 103/23 K/BB ratio in 108 career innings through age 20 and has yet to allow a home run in 420 plate appearances despite facing older competition in the vast majority of those matchups.

It's important to keep expectations in check for low-minors pitchers and Hu still needs to show that he can handle a full-season workload as a starter, but he's someone to keep an eye on this season and could rank much higher on this list next year. He was highly thought of as a prospect before signing, has fared very well against older competition at three different levels, and backs up the numbers with quality raw stuff.

Taylor Rogers went 13-18 with a 5.35 ERA in three seasons at the University of Kentucky, but the Twins picked him in the 11th round of the 2012 draft and now he's 26-16 with a 2.94 ERA in three seasons as a pro. His success has come despite mediocre strikeout rates, but that inability to miss bats against Single-A and Double-A hitters--and the lack of upside that suggests--is what keeps him from being considered a top prospect.

Last year at Double-A he posted a 3.29 ERA in 24 starts, but managed just 113 strikeouts in 145 innings for a rate below the Eastern League average. It wasn't all smoke and mirrors, though. Rogers had a good walk rate, allowed just four homers in 606 plate appearances, and induced lots of ground balls. And while he was much more effective against lefties than righties, the 6-foot-3 southpaw still held righties to a .367 slugging percentage with a 73/29 K/BB ratio.

Rogers was relatively young for Double-A at age 23 and his velocity has improved to the point that he regularly works in the low-90s, so he's certainly not without potential. Right now he projects as a back-of-the-rotation starter, but an uptick in strikeouts or improved control to go along with the strong ground-ball rates would give him mid-rotation upside. Either way, he's a candidate to reach the majors in 2015 and the Twins' decision-makers generally speak highly of him.

Adam Walker's power potential is undeniable. He put up big college numbers at Jacksonville to get picked by the Twins in the third round of the 2012 draft, went deep 14 times in his 58-game debut at rookie-ball, and led his league in homers during each of his first two full seasons. Last year his 25 homers for Fort Myers led the Florida State League and no one else managed even 20 long balls. Walker can hit the ball over the fence.

Unfortunately his inability to control the strike zone stands out almost as much. He's struck out a lot and rarely walked dating back to college and as a pro he's whiffed 347 times in 319 games. That's a red flag, especially when he's already 23 years old and has yet to face competition above Single-A. Walker showed a bit more selectivity last year with 44 walks in 555 plate appearances, but that came with 156 strikeouts and led to a lowly .246 average and .307 on-base percentage.

Most high-strikeout sluggers in the majors didn't actually strike out a ton in the minors because striking out a ton in the minors usually leads to failing in the majors. Walker needs to cut down on his strikeouts or at least learn to draw walks at a much higher rate or his 30-homer power will be wasted. He's a good athlete with above-average speed for a corner outfielder and should be a plus defensively, so if the strike-zone control clicks at some point he has plenty of all-around upside.

After beginning his pro career as a 30th-round draft pick and mediocre starter prospect Michael Tonkin shifted to the bullpen full time in 2011 and has looked like a late-inning reliever prospect ever since. He's split each of the past two years between Rochester and Minnesota, posting a 3.48 ERA with 82 strikeouts in 78 innings at Triple-A and a 3.26 ERA with 26 strikeouts in 30 innings in the majors. At age 25 he's deserving of extended chance in the Twins' bullpen for 2015.

Tonkin is a sturdy 6-foot-7 with the velocity to match his size, averaging 94 miles per hour with his fastball in the majors. He also throws a sharp, mid-80s slider that has already proven to be a plus pitch against big-league hitters by generating swinging strikes and ground balls. He's allowed a total of just 13 homers in 278 innings between the minors and majors over the past four years, including no more than four homers in a season.

Tonkin has top-notch raw stuff, misses plenty of bats with his fastball-slider combo, and unlike lots of hard-throwing reliever prospects he actually throws strikes too. His career walk rate is a very reasonable 2.5 per nine innings, including 2.3 at Triple-A and 2.7 in the majors. By this time next year there's a decent chance Tonkin will be entrenched as Glen Perkins' primary setup man and will have his own identity rather than being known as Jason Kubel's brother-in-law.

Brian Gilbert split the 2011 and 2012 seasons between Seton Hall University's rotation and bullpen with mediocre results, but switched to relief work full time in 2013 and thrived in the closer role with a 2.40 ERA, .198 opponents' batting average, and 49 strikeouts in 49 innings. Drafted by the Twins in the seventh round, he signed for $120,000 and predictably dominated inexperienced hitters in the low minors during his pro debut.

He made six rookie-ball appearances and 13 more at low Single-A, posting a 0.78 ERA and 14/1 K/BB ratio in 23 innings while allowing zero homers after serving up just one long ball last year at Seton Hall. Gilbert issued 22 walks and uncorked six wild pitches in 49 college innings, so his control in the low minors was a surprise. Baseball America's pre-draft scouting report pegged his fastball at 92-95 miles per hour, but noted that his off-speed pitches need improvement.

College relievers tend to move quickly through a farm system if they perform well, so hopefully the Twins test Gilbert against some more experienced hitters and see if his raw stuff translates into missed bats higher up the organizational ladder. They also drafted his Seton Hall teammate, outfielder Zack Granite, in the 14th round and he hit .285/.362/.343 with 14 steals in 61 games at rookie-ball.

Corey Williams took a step backward last season, but it wasn't as big as his ERA jumping from 3.47 to 5.16 would suggest. Most of his secondary numbers remained similar, but the problem is that he spent a full season being sub par at high Single-A as a 22-year-old in his third pro season and hasn't improved upon his poor control since being drafted in the third round by the Twins out of Vanderbilt University in 2011.

Williams has totaled 125 strikeouts in 121 pro innings, which is good but not great for someone the Twins hoped would develop into a mid-90s throwing, late-inning reliever. More troubling are his 63 walks in 121 innings, along with a relatively high 12 homers allowed and struggles versus right-handed hitters. Last season righties had an .823 OPS against Williams and he also failed to shut down lefties after holding them to a .179 batting average in 2012.

This is a key season for Williams, who once signed for $575,000 but now appears to be on the verge of falling into the potential middle reliever or situational left-hander pile, which isn't home to many actual prospects. He throws hard, induces plenty of ground balls, and misses a fair number of bats, but his actual results have been underwhelming dating back to college and there is no shortage of intriguing relief prospects throughout the Twins' farm system.

University of Kentucky pitchers have been popular Twins targets in recent drafts and that includes selecting left-hander Taylor Rogers in the 11th round two years ago. Rogers' college numbers were actually very ugly, as he went 13-18 with a 5.35 ERA while posting an ERA above 4.50 in all three seasons, but he's nearly halved that with a 2.69 ERA in two years as a pro. However, he's done that against Single-A hitters and with a high-80s fastball his prospect status is questionable.

Rogers' strikeout rate was very good at rookie-ball and low Single-A, but he's managed just 83 strikeouts in 131 innings at high Single-A and it's tough to take seriously a pitching prospect who can't crack six strikeouts per nine innings in the Florida State League. His control also hasn't been especially good, with 2.2 walks per nine innings at high Single-A, but Rogers did induce lots of ground balls while serving up a total of just five homers in 528 plate appearances there.

There are certainly plenty of soft-tossing lefties with poor strikeout rates who do just fine the big leagues, but for the most part they tended to have decent strikeout rates in the minors. Rogers shouldn't be written off as a total non-prospect and can do away with a lot of skepticism if he thrives at Double-A this season as a 23-year-old, but the odds are stacked against him and he lacks upside.

Two years ago the Twins drafted Rice University co-closers J.T. Chargois in the second round and Tyler Duffey in the fifth round. Chargois' career has been derailed by elbow surgery, but Duffey transitioned from reliever to starter at low Single-A last season with a lot of success, starting nine games with a 2.78 ERA and 47/6 K/BB ratio. Unfortunately he was considerably less impressive after being promoted to high Single-A and finished the year in the bullpen.

As a reliever at Rice and in his rookie-ball debut Duffey racked up tons of strikeouts, but last year as a starter he missed fewer bats and instead relied on very good control with an 83/20 K/BB ratio in 111 total innings. Those numbers match his raw stuff, which includes a low-90s fastball and slider/changeup off-speed repertoire, so it'll be interesting to see how long the Twins stick with Duffey as a starter.

Selecting college relievers and trying to turn them into professional starters was the focus of the Twins' draft in 2012 (well, that and picking some guy named Byron Buxton), but so far none of them have emerged as a standout starter prospect. Duffey and third-rounder Mason Melotakis look like the best bets right now, while Chargois and supplemental first-rounder Luke Bard have barely gotten out of the gates due to injuries.

Brett Lee was drafted in the late rounds by the Pirates in 2009 and the Dodgers in 2010 before signing with the Twins for $150,000 as a 10th-round pick out of St. Petersburg College in 2011. He had an excellent pro debut at rookie-ball in 2012 and then moved up to full-season competition last year, thriving at low Single-A with a 2.95 ERA and 89/26 K/BB ratio in 116 innings for Cedar Rapids.

Lee had the sixth-best walk rate in the Midwest League among all pitchers with at least 15 starts, but his strikeout rate of 6.9 per nine innings was actually below the league average of 7.6. Those numbers suggest that Lee is just another soft-tosser, of which the Twins never have a shortage, but he's actually a 6-foot-4 left-hander with decent velocity. Whether or not that ever translates into more missed bats is a key question for Lee's development.

Another reason to possibly be more excited about Lee's season than his overall numbers show is that he put together a fantastic second half with a 1.41 ERA and 45/8 K/BB ratio in 57 innings while holding opponents to a .204 batting average and one homer. Still not as many missed bats as you'd like to see, but eight walks and one homer in 57 innings is some awfully good pitching to contact and his ground-ball rate was strong as well.